The invention concerns an anchor screw to be applied on the palatal vault or any other part of the mouth, more particularly of mandible and maxilla to anchor devices used in the orthodontic correction.
It is well known that the orthodontic technique provides for the application to the tooth to be treated one or more forces of predetermined strength and the direction in order to correct the attitude for aesthetic reasons or even masticatory function.
The forces are transmitted to the tooth to be treated through orthodontic devices generally consisting of wires, bars or other mechanical traction and/or thrust elements.
These orthodontic devices are generally anchored through auxiliary external devices to anchoring zones outside the mouth or they can be connected to endoosteal implants inside the mouth or tooth screws fixed in the alveolar, palatal, zygomatic bone and so on. These screws have an anchoring function and have a lower threaded portion screwed to the bone, an upper portion provided with movement means to screw and unscrew said screw in the alveolar, palatal arch and so on and a central portion protruding from the gum to which said orthodontic devices are anchored.
More particularly the central portion of the known orthodontic screws is substantially cylindrical and allows to the orthodontic devices such as wires, to be wound perimetrically.
The known technique provides that the orthodontic correction devices are fixed to the above mentioned anchor screws simply rolling up a wire end for instance in the central cylindrical portion of said screw so as to warrant the static stability required to develop the traction or thrust forces adapted to bring the treated tooth in the correct position.
The main drawback is due to the poor-friction created between the orthodontic devices (wire) and the central portion of said screw, therefore the little friction required to with stand the traction and/or thrust forces.
A further drawback is also due to the difficulty to control when applying the orthodontic devices, the traction and/or thrust applied to said tooth, this difficulty arising from the fact of rolling up the wire on the central portion of the anchor screw.
Another drawback is due to the increase of the size of the anchor screw because of the wire rolled up around the central portion. WO 96 12451 A discloses an anchor screw for orthodontic correction treatments in which the anchorage of the orthodontic traction and/or trust devices is permitted by the cooperation of a cylindrical central portion of the screw with a cap superimposed at the end of said screw. FR-A-2681777 discloses and anchor element for orthodontic correction having an upper portion adapted to allow the anchorage of orthodontic traction and/or trust devices.
Other types of screws intended for the same object have shaped heads with grooves in which the terminal parts of the wires of the orthodontic devices may be fixed. A cap threaded on the screw head fixedly blocking the orthodontic wires is also provided.
Such a screw has the drawback of a high cost and also a considerable bulk in the mouth, as well as poor practicality because some zones of the mouth are hardly accessible.
It is an object of the present invention to overcome said drawbacks.
More particularly a first object of the invention is to create an anchor screw that can be applied wherever there is an available bone, allowing a better control of the traction and/or thrust force applied to the tooth to be treated.
Another object is to provide an anchor screw allowing to diminish the bulk of the entire orthodontic system.
A further object is to create a screw with such as shape to allow a better efficiency for the cleaning interventions carried out by patient and required to avoid possible infections.
Last but not least object is to provide an orthodontic screw which is cost effective also in respect of the available performances.
Said objects are obtained by an anchor screw for orthodontic correction treatments the main features of which are according to claim 1.
Advantageously the invention allows a fine regulation also of the direction of the traction and/or thrust force applied on each tooth to be treated.
Furthermore the invention reduces the tedious feeling of the patient due to the presence of foreign elements inside the mouth.
A further advantage of the invention is to allow to anchor more orthodontic devices at the same time.
According to a preferred embodiment of the invention the zone with reduced diameter has a transverse hole in respect of the screw axis suitable for passage of wires or other orthodontic devices so as to improve the anchoring efficiency of said devices, and an easier connection between screw and wire as well.